The screening of subjects will continue in an effort to determine factors associated with root surface caries (RSC). During the coming year, enough data will have been collected to begin the formal testing of simple associations and possibly of more complex interactions. Additionally, the study of diabetics will be completed, a comparison of RSC in blue and white collar workers at the Gillette Corporation will be carried out and another special risk group may be assessed. Microbiologically, the work having to do with the characterization of root surface plaque in diseased and non-diseased subjects will go forward with particular attention to those micro-organisms which, so far, seem to distinguish the two groups. The layer assay of RSC lesions will continue until enough data have been collected to determine whether there is a characteristic microbiological profile to the lesion. Physio-chemical studies will be extended to determine the solubility of root mineral, compare demineralization in enamel and dentin, produce demineralization of root and enamel surfaces by direct colonization of mutant cells, and assess the cariogenic potential of protease deficient mutants of A. viscosus and A. naeslundii. The investigation of salivary proteins will focus primarily on the molecular basis for the adhesion-promoting effects of individual peptide sequences of the PRP. Work will be started on the molecular aspects of the adhesion-promoting activity of the salivary mucins of certain streptococcal strains. In the areas of histology and electron microscopy, histological processing of teeth already on hand will be completed and sections will be analyzed by light microscope. Root surface lesions will be examined by scanning electron microscopy with special attention to the area subjacent to the plaque. Additionally, tissues from a completed hamster study will be analyzed histologically and selected material from a completed rodent study, will be analyzed by SEM for type and location of microorganisms involved in root caries lesions. Finally, a pilot effort is proposed involving the use of non-human primates to determine the effectiveness of dentinal coating materials in preventing RSC and root abrasion.